Sun's "Ring of Fire" Stoked by Sound Waves

Stefan Lovgren
for National Geographic News
May 30, 2007

It has been a burning mystery for decades: Why is a thin, irregular region of the sun's atmosphere known as the chromosphere much hotter than the star's visible surface?

The answer, scientists recently proposed, could be stellar sound.

The temperature at the sun's surface layer, or photosphere, is about 10,000°F (6,000°C)—much cooler than its 27,000,000°F (15,000,000°C) interior.

But in the chromosphere, the region just above the photosphere, the heat spikes again to about 20,000°F (11,000°C).

"It's like getting warmer as you move away from a fire instead of cooler—certainly not what you expect," said Scott McIntosh, a researcher at Southwest Research Institute in Boulder, Colorado.

Now McIntosh and colleagues' studies show that magnetic fields send sound waves from the sun's interior shooting upward, creating fountains of hot gas that shape and power the chromosphere.

The researchers compared the phenomenon to standing in Yellowstone National Park and being surrounded by musical geysers that pop up at random, sending shrill notes and hot water shooting high into the air.

(Related: watch movies of solar structures in action, including images of sound waves moving through the sun.)

"There's a lot more wave energy leaking into the solar chromosphere than we previously thought," McIntosh said on Tuesday during a meeting of the American Astronomical Society (AAS) in Honolulu, Hawaii.

Sound and Fury

The chromosphere, or "color sphere," is so named because its higher temperatures cause the sun's hydrogen to emit reddish light.

Clouds of material from the chromosphere suspended above the sun can create a ruby-red "ring of fire" around a total solar eclipse.

Continued on Next Page >>


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